Osteoporosis Flashcards
What is osteoporosis?
A systemic skeletal disease characterised by:
- low bone mass
- micro-architectural deterioration of bone tissue
Resulting in bone fragility and susceptibility to fracture
List the classic fracture sites associated with osteoporosis?
Hip
Wrist (Colle’s fracture)
Vertebral
What is a Colle’s fracture?
A wrist fracture, often occurs after a fall on outstretched hand
Who gets osteoporosis?
Women much more than men
People over age 50
Prevalence increases with age
What are the risk factors of osteoporosis?
SHATTERED mnemonic
S - steroid use H - hyperthyroid, hyperparathyroid A - alcohol T - thin T - testosterone, low levels E - early menopause R - renal or liver failure E - erosive inflammatory bone disease (RA) D - dietary, low calcium or diabetes
Why does menopause cause osteoporosis?
Menopause = oestrogen depletion
Oestrogen usually restrains osteoclast action
No oestrogen means no restraint
The osteoclasts go mad and resorb more bone than they should
Osteoblasts can’t keep up with the osteoclasts
Net loss of bone
Why does inflammatory disease like RA cause osteoporosis?
Pro-inflammatory cytokines increase bone resorption
What endocrine diseases cause osteoporosis?
Hyperthyroidism + hyperparathyroidism
Thyroid and parathyroid hormone increase bone turnover
Cushing’s
Cortisol increased bone resorption AND induces osteoblast apoptosis
What causes decreased skeletal loading?
Lower weight
Immobility
Which drugs increase the risk of osteoporosis?
Steroids
Depo-Provera: a contraceptive
Aromatase inhibitors
Androgen deprivation
How do steroids increase the risk of osteoporosis?
Interfere with osteoblasts making them slower at making new bone
Interfere with body’s handling of calcium
What 3 things contribute to bone strength?
- Bone mineral density
- Bone size
- Bone quality
What 3 things contribute to bone quality?
- Bone turnover (clasts + blasts)
- Architecture
- Mineralisation
What is meant by ‘quiescence’ in the context of bones?
Stability, an equal balance between bone resorption and formation
What do osteoblasts do?
Form new bone
What do osteoclasts do?
Resorption (digestion) of bone
What happens to the trabeculae in osteoporosis?
Decrease in trabecular thickness
Loss of horizontal trabeculae
Decrease in strength of trabeculae
What is trabecular tissue?
The criss-cross network of thin extensions within bone
How is osteoporosis picked up?
Patients usually present following a fracture
They are tested for osteoporosis
Investigations of osteoporosis?
DEXA scan: looks at bone density, and from this given a T score
Blood:
- Calcium
- Phosphate
What is a DEXA scan?
Dual Energy X-ray absorptiometry
Measures how much X-ray has been lost as it travels through the bone
The more X-rays picked up on the other side, the less structure of the bone is left
Which areas should you scan in a DEXA scan?
The bones most at risk:
- hip
- spine
- distal radius
What is a T score?
A score calculated by comparing the result of the DEXA scan with the score of a gender matched young adult average
I.e. How much bone density have they lost since they were 20?
What classifications are given using the T score?
Normal
Osteopenia
Osteoporosis
Severe osteoporosis
What is osteopenia?
Lower than normal bone density but not severe enough to be osteoporosis yet
What lifestyle measures should you advise patients with osteoporosis to take?
Quit smoking
Reduce alcohol
Light exercise
Calcium and vit D rich diet or supplements
Fall prevention strategies
- home modification
Management of osteoporosis?
Lifestyle measures
Drugs:
- anti-resorptive
- anabolic
What two classes of drugs do we use to treat osteoporosis?
Anti-resorptives: decrease osteoclast activity and bone turnover
Anabolic: increase osteoblast activity and bone formation
Name some anti-resorptive drugs classes.
Bisphosphonates
Hormone replacement therapy
Denosumab
Which drug is the first line choice for treating osteoporosis?
Bisphosphonates
How do the bisphosphonates work?
They inhibit an enzyme in the chilsterol synthesis pathway
This interferes with the modification of prenylated proteins
Which means the osteoclasts don’t have the ruffled border they need to resorb bone
What is the suffix of the bisphosphonates?
-dronate
What type of drug is denosumab and how does it work?
A biologic
Its a monoclonal antibody to RANK ligand. Which binds to RANK preventing osteoclasts getting activated so they can’t resorb bone
Name an anabolic drug used to treat osteoporosis?
Teriparatide
How does teriparatide work?
Builds back bone where the bone had been lost
It improves the trabecular structure too
What is hormone replacement therapy?
A treatment given to relieve the symptoms associated with menopause
Restores the natural female hormones: oestrogen and progesterone
What are the symptoms of menopause?
Hot flushes Night sweats Vaginal dryness Loss of libido Stress incontinence Osteoporosis
What are the benefits of HRT?
Reduces risk of fractures
Stops progression of osteoporosis
Prevents menopausal symptoms
Reduces risk of colon cancer
What are the risks of HRT?
Breast cancer Stroke CVS disease DVT Vaginal bleeding
